Update faucet instructions

[sschiessl-bcp]

Wait for BitSpark to upstream their changes to the faucet, refine and polish the text on http://dev.bitshares.works/en/master/development/testnets/setup_faucet.html
and switch links to faucet and check dependencies.

[cedar-book]

When I started, I've asked who can provide the knowledge about this procedure and know what we recommend. If anyone has the information about a better way to do this setup, please share.